Audit & provenance

ARCNM quotes are defensible. Every quote comes back with the cost broken down to the line item, the lot-size curve behind it, the cost drivers ranked by contribution, the machine it was priced on and why, and a prediction interval around the number. When a procurement team asks "how did this part get to €12.84?", you answer in 30 seconds, not a week.

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What a quote carries

GET /api/v1/calculations/{id} returns the result plus an analytics object with the audit detail. The stable top-level fields (unit_cost, total_cost, setup_cost, currency, status, timestamps) are documented in the Calculations reference; the analytics object carries the breakdown below.

analytics is informational — treat its keys as illustrative and don't hardcode the exact shape. The stable top-level fields are the contract.

{
  "id": "9d3f…",
  "status": "succeeded",
  "unit_cost": 12.84,
  "currency": "EUR",
  "analytics": {
    "cost_decomposition": { /* per-unit cost, line by line */ },
    "time_breakdown":     { "setup_time_s": 42.0, "cycle_time_s": 18.5, "unit_time_s": 19.2 },
    "lot_size_curve":     { "points": [ /* … */ ], "breakpoints": [ /* … */ ] },
    "unit_cost_interval": { "lo": 12.20, "hi": 13.50 },
    "selection":          { "machine_name": "…", "rationale_text": "…" },
    "extraction":         { "feature_count": 23, "pmi_count": 14, "dfm_issue_count": 1, "fusion_conflict_count": 0 },
    "cost_drivers":       { "drivers": [ /* … */ ] },
    "review":             { "needs_human_review": false, "reasons": [ ] }
  }
}

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Cost decomposition

cost_decomposition splits the unit cost into the line items that make it up — material_cost, machine_cost, labour_cost, programming_cost, tooling_cost, inspection_cost, finishing_cost — then direct_unit_cost and the overhead_var / overhead_fixed on top. See Cost & lot size.

Lot-size curve

lot_size_curve.points gives the modelled unit cost (unit_cost_eur) at each quantity; breakpoints flags the quantities where the unit cost changes slope, each with a plain-language rationale ("setup amortises across the lot at n=50"). A 1-off and a 1000-off can even pick different machines — the breakpoints are where that happens. See Cost & lot size.

Cost drivers

cost_drivers.drivers ranks the features that drive the unit cost. Each carries a rank, the feature_kind (e.g. pocket, hole), a human label, the cost_eur and cost_share it contributes, and reasons. Feed it straight back to your designers as value-engineering: "the four M3 tapped holes are 38% of the cost — relax them and the part drops to €9.10."

Machine selection

selection.machine_name is the machine the part was priced on; selection.rationale_text is the plain-language reason it was chosen.

Prediction intervals

Every quote carries a unit_cost_interval — a lo/hi band the true cost is expected to fall within. It tightens as an environment accumulates calibration evidence (see Calibration & environments). Use the half-width (hi - lo) / 2 to set a margin buffer, or trigger a re-quote when it's too wide for the customer.

Extraction summary & review flags

extraction reports the headline counts a buyer acts on — feature_count, pmi_count, dfm_issue_count, and fusion_conflict_count (how many fields the 3D model and the 2D drawing disagreed on). review.needs_human_review is true when the extraction or the price warrants a human look, with reasons in plain language — gate your auto-accept on it. See Extraction.

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Immutability

Every successful calculation row is append-only:

• The analytics field is read-only after the quote completes.
• Re-running the same part_revision_id + costing_environment_id + lot_size + material is not idempotent — it creates a new Calculation row with a new id, so calibration changes stay visible.
• The previous row stays accessible by id forever.

For "the price as it was on 2026-05-28" queries, persist the calculation_id in your ERP and re-fetch from us — we keep them.